In order to efficiently utilize light, reflectors have been used in various situations, and in recent years, switching to semiconductor light sources, namely, semiconductor laser and light emitting diode (referred to as “LED” hereinafter), has been promoted for the purpose of downsizing devices and light sources. On that account, not only mechanical strength is required of the reflectors but also excellent heat resistance and capability of being precisely molded are required of the reflectors because surface mounting of the reflectors onto printed wiring boards and the like is carried out. Moreover, a stable and high reflectance is required of the reflectors from the viewpoint of a function of light reflection, and it is necessary to inhibit lowering of reflectance caused by heating particularly in fabrication of LED and a reflow soldering process.
In this field, materials capable of withstanding reflow soldering at a temperature of 260° C. using a lead-free solder are necessary, and therefore, limited resins such as LCP (liquid crystal polymer) and polyamide resins are employed. Of the resins, LCP has a problem that a sufficiently high reflectance cannot be obtained as a reflector because it has low whiteness of a resin. On the other hand, aliphatic polyamides (PA6, PA66, PA11, PA12) having excellent strength properties and injection moldability, which have been widely used as the polyamide resins in the past, do not have sufficient heat resistance to resist the temperature of the reflow soldering process and sufficient low-water absorption properties. Moreover, they have another problem of lowering of reflectance because they are discolored when heated.
In patent documents 1 and 2, polyamide resins for light emitting diode reflectors, which use 1,9-diaminononane as a diamine component, are disclosed. These polyamide resins, however, are not satisfactory in the prevention of lowering of reflectance caused by heating in fabrication of LED, a reflow soldering process and the like.
Patent document 1: WO 03/085029
Patent document 2: Japanese Patent Laid-Open Publication No. 228776/1995